STRUCTURE, FUNCTION, & MAINTENANCE STANDARD SWING MOTOR 12 RELIEF VALVE PORTION 1) Outline The relief portion consists of check valves (2) and (3), shuttle valves (4) and (5), and relief valve (1). 2. Function When the swing is stopped, the outlet port circuit of the motor from the control valve is closed, but the motor continues to rotate under inertia, so the pressure at the output side of the motor becomes abnormally high, and this may damage the motor. To prevent this, the abnormally high pressure oil is relieved to port S from the outlet port of the motor (high-pressure side) to prevent any damage. 3.
Operation 1) When starting swing When the swing control lever is operated to swing right, the pressure oil from the pump passes through the control valve and is supplied to port MA . As a result, the pressure at port MA rises, the starting torque is generated in the motor, and the motor starts to rotate. The oil from the outlet port of the motor passes from port MA through the con- trol valve and returns to the tank. (Fig. 1) 2) When stopping swing When the swing control lever is returned to neu- tral, the supply of pressure oil from the pump to port MA is stopped.
With the oil from the outlet port of the motor, the return circuit to the tank is closed by the control valve , so the pressure at port MB rises. As a result, rotation resistance is gener- ated in the motor, so the braking effect starts. If the pressure at port MB becomes higher than the pressure at port MA , it pushes shuttle valve A (4) and chamber C becomes the same pressure as port MB . The oil pressure rises further until it reaches the set pressure of relief valve (1). As a result, a high braking torque acts on the motor and stops the motor. (Fig.2) When relief valve (1) is being actuated, the relief oil and oil from port S passes through check valve B (3) and is supplied to port MA .
This prevents cavitation at port MA . 10-96 PC210/240-7K